Oil sands are mined from the ground and fed to conveyors forming a stream that is processed downstream for extracting bitumen to produce oil. The stream of oil sands is composed of four main components: sands (e.g. quartz sand), water, clay and heavy oil or hydrocarbons (called bitumen). Calculating accurately the amounts of each of these components present in the oil sands stream is important because it can help predict and improve the extraction recovery of oil sands and control the oil production process. For example, clay seams are common and interfere with the conventional extraction methods and it would useful to measure more accurately the amount of clays in the oil sands stream extracted from the ground.
Among the known methods used for analyzing the composition of the extracted oil sands are near infrared (NIR) and radio spectrometry. Both are used to assess the concentration of constituents in oil sands where the reflectance spectra range from 1100 nm to 2500 nm and the specific oil sands components have specific wavelengths, for example 1400 nm for water, 1720 nm for oil, 2200 nm for kaolinite. Canadian patent application number 2834980 describes, for example, a method for analyzing a bitumen-containing process stream including directing a beam of infrared light at the stream, capturing the light corresponding to the infrared light after its interaction with the bitumen-containing process stream, and analyzing the captured light to obtain a spectrum. The composition estimate can be generated based on the obtained spectrum and a calibrated model. The disadvantage of the NIR and radio spectrometry methods is that they do not measure the actual amounts of the elements present in the oil sands, but rather estimate the amounts of some individual oil sands components such as oil, water and some clays using their associated wavelengths.
Another method used in the mining industry is the spectroscopic analysis of oil sands, which uses the signals containing information about the images of the ore sample to create a real time ore grade visualization including a composite overlay image of the ore sample, as described, for example, in United States patent application number 20140347472. This technology does not measure any oil sands components, but rather estimates the grade of the oil.
Furthermore, nuclear magnetic resonance pulse spectrometry can be used to analyze oil sands composition by initially saturating the magnetization of the oil sand sample and then subjecting the samples to a sequence of radio-frequency pulses optimized for the measurement of bitumen and water in the sample, as described in U.S. Pat. No. 8,547,096. The amount of bitumen and water is determined based on a partial least squares optimization based chemometric model. This technology can not be used to obtain information about certain components that might be present in the oil sands, for example the amounts of different clays.
The oil content in oil sands can also be measured using an acoustic technique, by observing the nonlinear dissipation phenomenon that is generated by the sound wave spreading in the oil sands. The oil saturation degree of the oil sands sample can be determined from the relative growth factor G and the nonlinear dissipation factor Alpha through a backward deduction method as described for example in the Chinese patent application number 101334380. However, this method also fails to measure the information related to certain components that might be present in the oil sands, for example information related to the amount of clay material.
There are also other methods for analyzing materials extracted from an earth formation. Prompt gamma neutron activation analysis (PGNAA) is one such method that is generally used to determine metal contents of ores. PGNAA has also been used to detect a clay parameter indicating, for example, a weight percentage of clay particles in an oil sand tailings stream, as described for example in Canadian patent application number 2909029.
In another method which involves using pulse neutron spectroscopy, the composition of the hydrocarbon material in the material extracted from an earth formation can be calculated based on the at least one gamma ray spectrum detected at the pulse neutron spectroscopy tool which emits a plurality of pulses of high-energy neutrons into the portion of the hydrocarbon material diverted and stored into a container, as described in Canadian patent application 2672018.
The known methods for analyzing the oil sands composition, described above, are only estimating certain components of oil sands or can only be used for detecting the composition of oil sand samples.
Therefore, there is still a need for a system and a method for real time, on-stream analysis of oil sand composition that can measure all the components of an oil sand stream (water, sand, hydrocarbon and clay) more accurately and in a continuous manner.